The present invention is directed to a load control structure for a work vehicle.
A conventional load control structure for work vehicles included one that controlled the motor operating means such that the swash plate of the variable displacement motor is moved from a higher speed position to a lower speed position when the engine load rises beyond a first predetermined value and such that the swash plate of the variable displacement motor is moved from the lower speed position to the higher speed position when the engine load decreases below a second predetermined value (see, for example, JP 6-17928), or one that controlled the operation of the pump operating means, based on detected information from the load detection means and detected information from the swash plate position detecting means, such that the greater an engine load is, greater is the extent to which the swash plate of the variable displacement pump is operated to a low speed side.
A control of the variable displacement pump based on load is suitable for operations with relatively small engine load and a control of the variable displacement pump based on load is suitable for operations with relatively large load. However, in the conventional systems as described above, no structure was provided that was suitable over a wide range of operational load from a small engine load to a large engine load.